The present invention relates to a method of ring opening cyclic diorganosiloxane comprising diorganosiloxy units having a polyfluoroalkyl radical attached to silicon by carbon-silicon bonds. More particularly, the present invention relates to the employment of water in combination with a strong acid catalyst, such as trifluoromethanesulfonic acid (triflic acid) to facilitate the polymerization of fluoroalkylsiloxane cyclic to provide fluoroalkylsiloxane homopolymer, copolymer and terpolymer fluids.
Ring opening polymerization of trifluoropropylmethylsiloxane cyclic trimer with trifluoromethanesulfonic acid has been described in Polymer Preprints, by G. Friends et al., Vol. 33, pages 493-494 August 1992, and Chang et al. Vol 33, pages 491-492. These publications, and Shintani et al, Japanese patent JPO 395,226, describe the formation of low viscosity fluoroalkylsiloxane copolymer fluids after long reaction times, such as 24 hours or more, at temperatures of 90.degree. C. or greater. In addition, as shown by U.S. Pat. No. 4,842,902, fluoroalkylsiloxane copolymers can be prepared by reacting cyclic diorganosiloxane, such as 1,3-divinyltetramethyl, or hexamethyl cyclic trimer together with diorganosiloxane hydrolyzate having terminal diorganofluoroalkylsiloxane units.
It would be desirable therefor to provide a procedure for making polyfluoroalkylsiloxane fluids, for example, fluid homopolymers, copolymers, and terpolymers, by effecting the direct ring opening polymerization of polyfluoroalkylsiloxane cyclics.
It also would be desirable to convert polyfluoroalkylsiloxane cyclics to polyfluoroalkylsiloxane fluids having viscosities in the range of 300-40,000 centipoise at 25.degree. C., while minimizing the formation of undesirable cyclics.
In addition, it would be desirable to make polyfluoroalkylsiloxane fluids at temperatures in the range of 20.degree. C. to 120.degree. C. within 4 to 10 hours.